The present invention is directed toward a heart monitoring device and more particularly toward such a device which is intended to be carried by a patient and which detects arrhythmias and records the patient's ECG in response thereto.
Cardiac monitoring apparatuses which detect arryhthmias have been known for many years. These are described, for example, in U.S. Pat. Nos. 3,144,019; 3,552,386; 3,587,563; 3,608,545; 3,823,708; 3,824,990; 3,881,467; 4,231,374; 4,261,370 and 4,457,315. It is known that the detection of two particular arrhythmias, tachycardia or high heartbeat rate and bradycardia or low heartbeat rate, are useful in providing information to a physician concerning the general condition of a patient's heart. Many of the foregoing patents describe systems for detecting tachycardia and/or bradycardia.
The systems described in the above patents are, for the most part, relatively sophisticated and are useful in a hospital environment and particularly in a cardiac care unit. These systems are not well suited for portable monitoring of ambulatory patients.
The apparatus described in U.S. Pat. No. 4,457,315 is specifically designed for use as a portable battery operated device to be carried by an ambulatory patient. While the device proposed in this patent would provide the desired benefits of portability not available with many of the prior monitors, it is not believed that the patented device has met with much succcess. This may be due to the relative complexity of the circuit thereby making the same relatively expensive. Furthermore, the circuit of the device shown in this patent utilizes an average over a series of heartbeats in order to determine the existence of an arrhythmia and, accordingly, is not capable of substantially instantaneously providing such an indication.